Combined analysis of resting regional wall thickening and stress perfusion with electrocardiographic-gated technetium 99m-labeled sestamibi single-photon emission computed tomography: Prediction of stress defect reversibility

Background  The high photon flux and stable distribution of the myocardial perfusion agent ^99mTc-labeled sestamibi allow the perfusion data to be acquired in an electrocardiographic (ECG)-gated mode, such that information on resting regional wall thickening may be obtained simultaneously with stress perfusion data. The objective of this study was to assess whether visual analysis of resting regional wall thickening provided by ECG-gated acquisition of ^99mTc-labeled sestamibi stress perfusion images correlates with and predicts the reversibility of stress-induced perfusion defects, potentially obviating the need for rest imaging. Methods and Results  Fifty-nine patients referred for myocardial perfusion imaging were studied with rest and stress single-photon emission computed tomographic (SPECT) sestamibi imaging, and the stress perfusion data were acquired in an ECG-gated mode. Visual analysis of the presence and reversibility of stress perfusion defects on standard imaging was correlated with the wall thickening data from the poststress gated SPECT images. Quantitative circumferential profile analysis of the short-axis images was performed to assess the influence of relative stress perfusion defect severity on the correlation between wall thickening and defect reversibility. Among the 72 segments with stress-induced perfusion defects and visually apparent wall thickening on ECG-gated SPECT images, 69 were reversible on rest imaging (positive predictive value of 96% for wall thickening to predict stress defect reversibility). Of the 35 segments with stress-induced defects and no apparent wall thickening on ECG-gated SPECT images, however, 14 (40%) demonstrated significant stress defect reversibility on rest imaging. This result represents a negative predictive value of only 60% for the lack of apparent wall thickening to predict correctly an irreversible stress defect. Among the segments with reversible stress perfusion defects and visually apparent wall thickening, relative stress sestamibi activity was higher (51%±10%, [percentage of peak]) than in segments with reversible stress defects and no visually apparent wall thickening (39%±4% of peak activity [p<0.0001]). Conclusions  Visual evidence of wall thickening by poststress ECG-gated SPECT sestamibi imaging in the territory of a stress-induced perfusion defect correlates highly with stress defect reversibility on rest imaging and may obviate the need to perform rest imaging, thereby potentially reducing the time and cost involved in myocardial perfusion imaging. The absence of visually apparent wall thickening, however, underestimates the prevalence of stress defect reversibility on rest imaging; in such instances, rest imaging must be performed to differentiate ischemia from infarction in the territory of a stress perfusion defect.     

Usefulness of gated SPECT myocardial imaging in evaluation of patients with inferior myocardial infarction

Objective

Gated single photon emission computed tomography (gated SPECT) myocardial imaging gives useful information about the extent and severity of perfusion abnormalities (PA) and global left ventricular (LV) function in patients with coronary artery disease. The aim of this study was to evaluate by gated SPECT myocardial imaging differences in perfusion scores and LV function between stress and rest in patients with mild left ventricular dysfunction and/or normal function and previous inferior myocardial infarction (IMI) and to detect myocardial stunning.

Materials and methods

The study included 77 patients (age 53 ± 8.21) with mild left ventricular dysfunction and previous IMI divided into two groups. Group 1 consisted of 34 patients with IMI and additional ischemia on perfusion scan and group 2 with 43 patients with previous IMI without ischemia on perfusion scan. All patients underwent a 2-day stress-rest gated SPECT myocardial imaging protocol with 99m technetium-methoxyisobutylisonitrile (^99mTc-MIBI).

Results

There was a more significant post-stress to rest decrease in ejection fraction (EFps) in patients with IMI and additional ischemia (group 1) than in patients with IMI (group 2) (?1.5 ± 2.5 vs. 1.5 ± 2.3, p < 0.001). In group 1, there was a significant increase in post-stress end-systolic volume (ESVps) in comparison to ESVr (70.4 ± 29.8 vs. 66.2 ± 26.2 ml, p = 0.044). However, the decrease in EF post-stress to rest did not reach the level of significance (51.7 ± 10.8 vs. 53.2 ± 10.2%, p = 0.147). The extent and severity of perfusion abnormalities were higher on stress (SSS) than on rest images (SRS) (13.9 ± 8.6 vs. 8.3 ± 7.8, p < 0.001). There was no difference in global LV parameters or perfusion abnormalities in patients in group 2 between stress and rest except for a significant increase in the post-stress EF to rest value (57.9 ± 11.9 vs. 56.2 ± 10.5%, p = 0.018). Severe decrease of post-stress EF to rest was found in 12 (16%) patients indicating stunning.

Conclusion

In patients with mild left ventricular dysfunction and IMI with additional ischemia there is evidence of a decrease in the post-stress EF with an increase in the post-stress ESV. In addition, a significant association between the decrease of post-stress EF with the extent and severity of perfusion abnormalities was detected. Gated SPECT myocardial imaging has an important role in the evaluation of perfusion and LV function in patients with IMI especially in patients with additional ischemia.     

Evaluation of simultaneous 201Tl/99mTc dual-isotope cardiac SPECT imaging with model-based crosstalk compensation using canine studies

Background

Simultaneous ²⁰¹Tl/^99mTc-sestamibi dual-isotope myocardial perfusion SPECT imaging can reduce imaging time and produce perfectly registered rest/stress images. However, crosstalk from ^99mTc into ²⁰¹Tl images can significantly reduce ²⁰¹Tl image quality. We have developed a model-based compensation (MBC) method to compensate for this crosstalk. The method has previously been validated with phantom and simulation studies. In this study, we evaluated the MBC method using a canine model.

Methods

Left anterior descending or left circumflex coronary artery stenoses were created in 50 adult mongrel dogs weighing 20-30 kg. The dogs were injected with 111 MBq (3 mCi) of ²⁰¹Tl at rest, and a SPECT study acquired. Stress was induced by administering adenosine to the dog, followed by injection of 740 MBq (20 mCi) of ^99mTc-sestamibi at peak stress. A second SPECT study was performed with data acquired in both ²⁰¹Tl and ^99mTc energy windows to provide simultaneous dual-isotope projection data. The images were reconstructed using the ordered-subsets expectation-maximization reconstruction algorithm with compensation for attenuation, scatter, and detector response. For simultaneously acquired ²⁰¹Tl data, we also applied the MBC method to compensate for crosstalk contamination from ^99mTc.

Results

Without compensation, ^99mTc crosstalk increased the estimated ²⁰¹Tl activity concentration in the rest images and reduced defect contrast. After MBC, the ²⁰¹Tl images were in good agreement with the registered single-isotope images and ex vivo count data. The ischemic (IS) to non-ischemic (NIS) region ²⁰¹Tl activity concentration ratios were computed for single-isotope and dual-isotope studies. The correlation with ex vivo IS-NIS ratios was 0.815 after MBC, compared to the 0.495 from data without compensation. In addition, the regression line for the IS-NIS ratios with MBC was almost parallel to the line of identity with a slope of 0.93, compared to a slope of 0.45 without compensation.

Conclusions

These results demonstrate that model-based crosstalk compensation can provide substantial reduction of crosstalk effects in simultaneously acquired myocardial perfusion SPECT images in living biological systems.     

Dose reduction in half-time myocardial perfusion SPECT-CT with multifocal collimation

Background

Recent technological advances in myocardial perfusion imaging may warrant the use of lower injected activity. We evaluated whether quantitative measures of stress myocardial perfusion defects using Tc-99m sestamibi and low-energy high-resolution (LEHR) collimators are equivalent to lower dose SPECT-CT with cardiac multifocal collimators and software (IQ·SPECT).

Methods

93 patients underwent one-day rest-stress gated SPECT-CT. Following conventional rest imaging, 925-1100 MBq (25-30 mCi) of Tc-99m sestamibi was injected during stress testing. Stress SPECT-CT images were acquired two ways: with LEHR (13 minutes) and IQ·SPECT (7 minutes). Low-dose IQ·SPECT stress was simulated by subsampling the full-dose data to half-, quarter-, and eighth-count levels. Abnormalities were quantified using the total perfusion deficit (TPD) score and dose-specific databases.

Results

The mean ± SD of the differences between LEHR and IQ·SPECT TPD scores were ?1.01 ± 5.36%, ?0.10 ± 5.81%, 1.78 ± 4.81%, and 1.75 ± 6.05% at full, half, quarter, and eighth doses, respectively. Differences were statistically significant for quarter and eighth doses. Correlation between LEHR and IQ·SPECT was excellent at all doses (R ≥ 0.93). Bland-Altman plots demonstrated minimal bias.

Conclusions

With IQ·SPECT, quantitative stress SPECT-CT imaging is possible with half of the standard injected activity in half the time.

     

Assessment of myocardial viability by dynamic tomographic iodine 123 iodophenylpentadecanoic acid imaging: Comparison with rest-redistribution thallium 201 imaging

Background

This study examined the ability of dynamic ¹²³I-labeled iodophenylpentade-canoic acid (IPPA) imaging to detect myocardial viability in patients with left ventricular (LV) dysfunction caused by coronary artery disease.

Methods and Results

Serial 180-degree single-photon emission computed tomographic (SPECT) images (five sets, 8 minutes each) were obtained starting 4 minutes after injection of 2 to 6 mCi ¹²³I at rest in 21 patients with LV dysfunction (ejection fraction [EF] 34%±11%). The segmental uptake was compared with that of rest-redistribution ²⁰¹Tl images (20 segments/study). The number of perfusion defects (reversible and fixed) was similar by IPPA and thallium (11±5 vs 10±5 segments/patient; difference not significant). There was agreement between IPPA and thallium for presence or absence (κ=0.78±0.03) and nature (reversible, mild fixed, or severe fixed) of perfusion defects (κ=0.54±0.04). However, there were more reversible IPPA defects than reversible thallium defects (7±4 vs 3±4 segments/patient; p=0.001). In 14 patients the EF (by gated pool imaging) improved after coronary revascularization from 33%±11% to 39%±12% (p=0.002). The number of reversible IPPA defects was greater in the seven patients who had improvement in EF than in the patients without such improvement (10±4 vs 5±4 segments/patient; p=0.075).

Conclusions

¹²³I-labeled IPPA SPECT imaging is a promising new technique for assessment of viability. Reversible defects predict recovery of LV dysfunction after coronary revascularization.     

A comparison of rest sestamibi and rest-redistribution thallium single photon emission tomography: Possible implications for myocardial viability detection in infarcted patients

Thirty patients (26 men, 4 women, mean age 61 ± 8 years) who had suffered myocardial infarction 15 ± 6 months previously, were submitted to (1) standard stress-redistribution thallium-201 single photon emission tomography (SPET), (2) rest-redistribution²⁰¹Tl SPET and (3) stress-rest technetium-99m sestamibi SPET. Uptake modifications in relation to exercise-induced defects were evaluated in a total of 390 myocardial segments. Tracer uptake was scored as normal (=0), mildly reduced (=1), apparently reduced (=2), severely reduced (=3) or absent (=4). Comparison of stress studies failed to show any statistical difference (58% segmental abnormalities with sestamibi vs 61% with thallium). Uptake abnormalities (score 1–4) were detected in 55% of the segments wiliest sestamibi, 55% with standard thallium redistribution, 55% with early imaging after thallium injection at rest and 54% with 3-h delayed rest imaging (P = NS). Absence of tracer uptake (score = 4) under resting conditions was recorded in 75 (19%) segments with standard²⁰¹Tl redistribution, 75 (19%) with rest sestamibi, 70 (18%) with rest²⁰¹Tl imaging and 62 (16%) with rst-rdistruion²⁰¹Tl (P<0.05 vs other imaging modalities). Thus, 3-h delayed rest thallium imaging detected reversibility of uptake defects in a significantly higher number of myocardial segments. This finding might have important implications for both tracer and technique selection when myocardial viability is the main clinical issue.     

A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT

Objectives

Wide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity.

Methods

In 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate “half-time” acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received “half-dose” rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise.

Results

Mean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for “full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for “half-time” WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for “half-dose” WBR. “Half-time” and “half-dose” WBR image quality were both superior to standard full-time OSEM (P’s < .001). There was no significant difference between the summed stress and rest scores for “full-time” OSEM vs “half-time” WBR in 82 patients with perfusion defects.

Conclusions

Both “half-time” and “half-dose” WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.     

Very low-activity stress/high-activity rest, single-day myocardial perfusion SPECT with a conventional sodium iodide camera and wide beam reconstruction processing

Background

A stress (S)/rest (R) 1-day Tc-99m sestamibi protocol is logistically advantageous and facilitates stress-only imaging. However, with conventional 370?MBq (10?mCi) S activity and subsequent 1,110-1,295?MBq (30-35?mCi) R activity there is a risk of S-to-R ??shine-through?? and underestimation of defect reversibility. New software methods cope with lower counting statistics and should allow for both a reduced S activity and also less likelihood of S-to-R ??shine-through.??

Methods

102 prospective patients [49 men, 53 women; mean weight 178?±?41 lbs (range 98-265?lbs); chest 41.5???±?4.0?? (range 32??-52??)] received 192.4?+?18.5?MBq (5.2?±?0.5?mCi) Tc-99m sestamibi S (25 exercise, 77 regadenoson) activity followed in 30-40?minutes by ??full-time?? (12?minutes) two-headed NaI camera S SPECT. Immediately thereafter, a 16-minute S SPECT acquisition was also performed in 37/102 patients. Then at 60-80?minute post-S all patients received 1328.3?+?129.5?MBq (35.9?±?3.5?mCi) Tc-99m sestamibi, and ??half-time?? (7.5?minutes) R SPECT was acquired. All tomograms were processed with wide beam reconstruction (WBR, UltraSPECT Ltd.) software. A time-adjusted R/S myocardial count density ratio (MCDR) was calculated using automated software. S SPECT quality was visually graded (poor, fair, good, excellent) based upon myocardial definition, cavity contrast, RV visualization, and noise. For comparison, the S/R MCDR was calculated in 581 consecutive patients undergoing a conventional 370?MBq R/1110?MBq S (10?mCi R/30?mCi S) protocol.

Results

S SPECT was normal in 44 patients (43%). Image quality was good-excellent in 93 (91%) patients with 12-minute S SPECT. Also in 37 (98%) patients with 16-minute S SPECT, quality was good-excellent. In patients with >42?? chests 12-minute S SPECT quality worsened with increasing chest circumference, manifested by myocardial ??blurring.?? Image quality improved by ??1 grade in the 12/37 patients (32%) also undergoing 16-minute S SPECT. The time- and decay-corrected 12-minute mean R/S MCDR was 5.78, a ratio adequate to minimize S-to-R shine-through, as verified in phantom experiments, and significantly better than a 3.79 S/R ratio achieved in the 581 patients undergoing a conventional R/S protocol.

Conclusions

An approximately 185?MBq (5?mCi S) Tc-99m SPECT processed with WBR provides adequate image quality. For larger patients prolonging image acquisition to 16?minutes is beneficial. For patients with normal S SPECT, a S-only protocol is feasible, affording them a very low (approximately 1.4?mSv) radiation dose. If subsequent R SPECT is necessary, it can be performed with approximately 1,332?MBq (36?mCi) with minimal S-R ??shine-through.??     

Serial assessment of left ventricular function during dobutamine stress by means of electrocardiographygated myocardial SPECT: Combination with dual-isotope myocardial perfusion SPECT for detection of ischemic heart disease

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial single photon emission computed tomography (SPECT). The purpose of this study was to evaluate left ventricular performance during dobutamine stress by means of ECG-gated myocardial perfusion SPECT with short-time data collection. METHODS AND RESULTS: After administration of Tc-99m sestamibi or tetrofosmin (600-740 MBq), 67 patients with ischemic heart disease, including 35 with prior myocardial infarction, were examined by ECG-gated myocardial perfusion SPECT at rest and during dobutamine stress (at dosages of 4, 8, 12, 16, and 20 microg/kg/min, with increments every 8 minutes). The ECG-gated data collection time was 5 minutes for each dobutamine dosage. After acquisition of gated SPECT data at the highest dose, thallium 201 chloride (111 MBq) was injected, and dual-isotope SPECT was also performed to assess the myocardial ischemia. In 32 patients without prior myocardial infarction, the sensitivity of individual stenosed-vessel detection with dual-isotope perfusion SPECT, with wall motion abnormality obtained from gated SPECT, and with the combined method was 55.9%, 52.9%, and 73.5%, respectively, based on coronary angiography. ECG-gated SPECT during dobutamine infusion revealed regional wall motion abnormalities (worsening or biphasic response) in 19 (57.6%) of 33 infarcted areas with culprit coronary arterial stenosis. The prevalence of reversible perfusion defects on dual-isotope SPECT was higher in segments with wall motion abnormalities than in segments with normal wall motion response (89.5% vs 42.9%, P <.02). CONCLUSIONS: Myocardial perfusion and left ventricular function during dobutamine infusion were analyzed in a single examination by means of the combined method. This procedure has the potential to provide comprehensive information with which to evaluate patients with ischemic heart disease.     

Feasibility of a rapid protocol of 1-day single-isotope rest/adenosine stress Tc-99m sestamibi ECG-gated myocardial perfusion imaging

Background

We previously developed a new rapid protocol for single-isotope rest/adenosine stress technetium 99m sestamibi (MIBI) electrocardiography-gated myocardial perfusion imaging examination. The feasibility and limitations of this rapid protocol are unclear.

Methods and Results

We examined 422 patients who underwent rest acquisition, which eliminates the waiting time, after injection of low-dose MIBI and drinking 400 mL of water. The patients immediately underwent adenosine stress. Stress acquisition was performed 1 hour after injection of high-dose MIBI. The sensitivity and specificity for detecting significant coronary stenoses were 93% and 70%, respectively. The frequency of significant (moderate or severe) inferior wall artifacts on the rest single photon emission computed tomography images among all patients was 16.3%. The frequency of significant artifacts in patients aged 70 years or older was significantly lower than that in patients aged less than 70 years (11.9% vs 26.9%, P=.0001). Multivariate analysis revealed that age less than 70 years and prior myocardial infarction were predictors of significant artifacts on resting images (P<.0001 and P<.05, respectively).

Conclusions

Our rapid protocol for MIBI myocardial perfusion imaging (MPI) provides high-quality images and good patient throughput, and it is effective at reducing the total examination time.     

Fast technetium 99m-labeled sestamibi gated single-photon emission computed tomography for evaluation of myocardial function

Background

This study assesses the feasibility of ^99mTc-labeled sestamibi electrocardiographic gated single-photon emission computed tomography (SPECT) with a short acquisition time (6.7 minutes, “fast” gated SPECT) for the evaluation of stress myocardial perfusion and poststress myocardial function. Simultaneous assessment of stress perfusion and poststress function is possible with standard gated SPECT acquisition (19.3 minutes) of stress-injected sestamibi. Sestamibi gated SPECT can be used to evaluate regional wall motion (RWM), thickening, and left ventricular ejection fraction (LVEF); the feasibility of fast gated SPECT has not been evaluated previously.

Methods and Results

Fifty patients were studied who underwent treadmill exercise, sestamibi injection (25 to 30 mCi), and standard gated SPECT 15 minutes after exercise, immediately followed by fast gated SPECT. All patients underwent rest ²⁰¹TI SPECT before exercise testing. All studies were analyzed by semiquantitative visual scoring. Both standard and fast gated SPECT were read for stress perfusion and poststress wall motion and thickening, dividing the left ventricle into 20 segments, on a 5-point scale described previously. The measurement of LVEF used a previously described automatic algorithm. Average myocardial counts per pixel were 58±19 for standard gated SPECT and 13±4 for fast gated SPECT (p=0.0001). Heart/lung ratio was 10.2±4.8 for regular gated SPECT and 10.3±5.7 for fast gated SPECT (difference not significant). Perfusion analysis showed exact agreement in 92% of the segments (κ=0.76; p<0.01). Correlation between LVEFs measured from standard and fast gated SPECT was 0.94. Analysis of 998 segments (two segments were uninterpretable) showed exact agreement in 96% (κ=0.89; p<0.001) for RWM and 94% (κ=0.83; p<0.001) for thickening between standard and fast gated SPECT. In 225 segments with abnormal RWM and 189 segments with abnormal thickening by both standard and fast gated SPECT, exact agreements were 0.92 for RWM (κ=0.90; p<0.001), and 0.87 for thickening (κ=0.80; p<0.01).

Conclusions

Our data demonstrate that fast sestamibi gated SPECT is feasible and yields results equivalent to those of standard sestamibi gated SPECT with respect to left ventricular regional and global function.     

Impaired Coronary Flow Reserve Is the Most Important Marker of Viable Myocardium in the Myocardial Segment-Based Analysis of Dual-Isotope Gated Myocardial Perfusion Single-Photon Emission Computed Tomography

Objective

The aim of this study was to investigate the most robust predictor of myocardial viability among stress/rest reversibility (coronary flow reserve [CFR] impairment), ²⁰¹Tl perfusion status at rest, ²⁰¹Tl 24 hours redistribution and systolic wall thickening of ^99mTc-methoxyisobutylisonitrile using a dual isotope gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with coronary artery disease (CAD) who were re-vascularized with a coronary artery bypass graft (CABG) surgery.

Materials and Methods

A total of 39 patients with CAD was enrolled (34 men and 5 women), aged between 36 and 72 years (mean 58 ± 8 standard in years) who underwent both pre- and 3 months post-CABG myocardial SPECT. We analyzed 17 myocardial segments per patient. Perfusion status and wall motion were semi-quantitatively evaluated using a 4-point grading system. Viable myocardium was defined as dysfunctional myocardium which showed wall motion improvement after CABG.

Results

The left ventricular ejection fraction (LVEF) significantly increased from 37.8 ± 9.0% to 45.5 ± 12.3% (p < 0.001) in 22 patients who had a pre-CABG LVEF lower than 50%. Among 590 myocardial segments in the re-vascularized area, 115 showed abnormal wall motion before CABG and 73.9% (85 of 115) had wall motion improvement after CABG. In the univariate analysis (n = 115 segments), stress/rest reversibility (p < 0.001) and ²⁰¹Tl rest perfusion status (p = 0.024) were significant predictors of wall motion improvement. However, in multiple logistic regression analysis, stress/rest reversibility alone was a significant predictor for post-CABG wall motion improvement (p < 0.001).

Conclusion

Stress/rest reversibility (impaired CFR) during dual-isotope gated myocardial perfusion SPECT was the single most important predictor of wall motion improvement after CABG.     

Phase analysis by gated F-18 FDG PET/CT for left ventricular dyssynchrony assessment: a comparison with gated Tc-99m sestamibi SPECT

Purpose

To investigate the value of gated F-18 FDG PET/CT on left ventricular (LV) dyssynchrony assessment in comparison with gated Tc-99m sestamibi SPECT in patients with coronary artery disease (CAD).

Methods

The data of 100 consecutive CAD patients who underwent both gated myocardial Tc-99m sestamibi SPECT and F-18 FDG PET/CT imaging were analyzed. Phase standard deviation (SD) and histogram bandwidth (BW) were derived from phase analysis using Cedars software package. The correlation and agreement of SD and BW between Tc-99m sestamibi SPECT and F-18 FDG PET/CT were examined. Myocardial viability and the site of latest activation assessed by the two imaging methods were compared as well.

Results

A moderate correlation for SD (r = 0.58, p < 0.0001) and BW (r = 0.60, p < 0.0001) was found between gated SPECT and gated F-18 FDG PET/CT. Bland–Altman analysis revealed an overestimation of SD and BW (6.4° ± 14.3° and 22.0° ± 46.8°) by gated F-18 FDG PET/CT. Multivariate logistic regression analysis identified that significant LV remodeling on SPECT imaging, LV functional parameters and F-18 FDG uptake ratio of myocardium to blood pool (SUV_M/B) were associated with the overestimation. Myocardial SPECT and F-18 FDG PET/CT had a 67.1 % identity in determining the latest activation site and 5.2 % more viable myocardium was detected by F-18 FDG PET/CT than SPECT.

Conclusion

Gated F-18 FDG PET/CT moderately correlated with gated Tc-99m sestamibi SPECT in assessing LV dyssynchrony. Gated F-18 FDG PET/CT phase analysis should be cautiously applied in CAD patients with significant LV remodeling on SPECT imaging, severe LV functional impairment or poor myocardial F-18 FDG uptake.     

Prognostic value of tomographic rest-redistribution thallium 201 imaging in medically treated patients with coronary artery disease and left ventricular dysfunction

Background

Previous studies show that rest-redistribution thallium imaging is useful in the assessment of myocardial viability. The impact of such studies on patient outcome is not well defined. This study examined the prognostic value of tomographic rest-redistribution ²⁰¹TI imaging in 81 medically treated patients with coronary artery disease and left ventricular dysfunction.

Methods and Results

Rest-redistribution single-photon emission computed tomographic images were obtained and analyzed quantitatively. The segmental thallium uptake (20 segments per patient) was interpreted as normal, reversible defect, mild to moderate fixed defect, or severe fixed defect. The thallium images were abnormal in 80 patients. The left ventricular ejection fraction was 27%±8% in patients with no redistribution and 26%±7% in patients with redistribution (difference not significant). In patients with no ischemia, there were 7±5 severe fixed defects and 5±4 mild to moderate fixed defects per patient. In patients with ischemia there were 7±4 reversible defects, 3±3 mild to moderate fixed defects, and 5±4 severe fixed defects per patient. The number of any abnormal segments was 11±5 in patients with no ischemia and 14±4 in patients with ischemia (p=0.03). During a mean follow-up of 31±24 months, there were 11 cardiac deaths in patients with no ischemia (26%) and 22 in patients with ischemia (58%); the survival rate was worse in patients with than without ischemia (p<0.05). Multivariate Cox survival analysis on important clinical, angiographic, and thallium variables showed that the presence of redistribution was an independent predictor of death (x ²=5; p=0.03).

Conclusions

Patients with left ventricular dysfunction and redistribution on rest thallium imaging, a marker of hibernating myocardium, have a higher mortality rate with medical therapy than do patients with a comparable degree of left ventricular dysfunction but with fixed defects only. Thus observations similar to those made with positron emission tomography can be made in a much more straightforward, simple, and probably cost-effective manner with single-photon emission computed tomography.     

Technetium 99m sestamibi in the assessment of chronic coronary artery disease.

Extensive work has already been performed with regard to both planar and single photon emission computed (SPECT) technetium 99m sestamibi studies. Before widespread application of optimized acquisition and processing methods, clinical results between 99mTc sestamibi and thallium 201 were remarkably similar. It is anticipated that as techniques for 99mTc sestamibi planar and SPECT imaging become optimized, improvements in sensitivity and specificity for detection of coronary artery disease, over those observed with 201TI, might be forthcoming. This expectation is based on the improved image quality inherent in the use of the 99mTc agent with its higher count rate and higher energy. This improvement in image quality may be a principal reason for laboratories to switch from 201TI to 99mTc sestamibi imaging. It is anticipated that, with improved imaging characteristics, it will be easier for the average community hospital to obtain higher quality planar or SPECT imaging using 99mTc sestamibi rather than 201TI. In addition to improved image quality, the characteristics of 99mTc sestamibi allow gated planar or SPECT perfusion images to be obtained. It has been suggested that stress-gated SPECT sestamibi studies may provide all the information contained in a stress-rest nongated 99mTc sestamibi study, thereby potentially increasing patient throughput, a major concern with SPECT. Throughput can also be increased by using dual-isotope approaches with rest 201TI and stress technetium sestamibi acquisitions, employing either separate or simultaneous imaging with which the entire study can be accomplished in less than 2 hours. With simultaneous dual-isotope acquisition, camera time can be reduced by 50%. Finally, 99mTc sestamibi offers the advantage of the ability to perform first-pass exercise ventricular function and SPECT myocardial perfusion studies with a single injection of tracer. Regarding the assessment of myocardial viability, results to date suggest a very high degree of concordance between 201TI and 99mTc sestamibi studies using either planar or SPECT acquisition techniques. Correlative rest studies with both tracers will be of particular interest, as will preoperative and postoperative and position emission tomography correlation studies.     

Does location matter? Prognostic value of single-photon emission computed tomography myocardial perfusion imaging by vascular territory

Background

The location of a myocardial perfusion abnormality frequently affects clinical decision making, especially if the left anterior descending artery (LAD) territory is involved. The purpose of this study was to determine whether the location of abnormalities on single-photon emission computed tomography (SPECT) imaging affects outcomes.

Methods

We retrospectively analyzed 21,294 consecutive patients with known or suspected coronary artery disease who underwent exercise or pharmacological stress SPECT over a 10-year period. Using the ASNC 17-segment model, 2 observers interpreted images with regards to defect severity, size, and reversibility. The summed stress score (SSS) was used in relation to vascular territories [LAD, right coronary artery (RCA), and left circumflex artery (LCx)]. All patients were followed over a mean period of 2.5?±?2?years for cardiac events (cardiac death or non-fatal myocardial infarction).

Results

Of the enrolled patients, 5,676 had single-vessel territory defects with a mean SSS of 4.3?±?2.8. Cardiac event-free survival curves revealed no significant difference between the 3 locations (LAD, RCA, and LCx) (P?=?.235). When compared by mild (2-3), moderate (4-8), or severe (>8) SSS, outcomes between the 3 groups were again similar. There were 2,907 patients with two-vessel territory defects with a mean SSS of 10.8. Outcomes were similar between the following 2 groups: two-vessel with LAD involvement and two-vessel without LAD involvement (P?=?.558).

Conclusion

In patients with single- or two-vessel territory perfusion abnormalities with similar size and severity of perfusion defects, the location of defect did not impact future cardiac events. Location of myocardial perfusion defect on SPECT imaging may not be helpful in clinical decision making.     

Dual isotope myocardial scintigraphy (201thallium at rest/99 M technetium tetrofosmin with exercise) in the detection of reversible hypoperfusion

The dual-isotope technique (rest 201Tl and stress 99mTc-sestamibi) is useful to assess myocardial perfusion in coronary disease patients. 99mTc-labeled tetrofosmin is a radiopharmaceutical whose characteristics are similar to sestamibi. Thus, we decided to use it to detect reversible myocardial hypoperfusion in patients with a background of myocardial infarction and ischemia. A sequential dual-isotope scintigraphy (3 mCi rest 201Tl and 25 mCi stress 99mTc-tetrofosmin) with 24-hour 201Tl redistribution (RD) was performed in 20 patients with previously confirmed myocardial infarction and clinical and ergometric signs of ischemia. Each patient also underwent a stress-redistribution protocol with redistribution at 4 and 24 hours post injection with 201Tl scintigraphy within two weeks of the first study. The qualitative uptake analysis showed no significant differences in the number of myocardial segments with severe reduction of tracer uptake on stress that improved at rest or in RD images, even if 24-hour RD images were considered. The quantitative global uptake analysis showed a similar defect reversibility with both protocols; however if 24-hour RD images were considered the uptake improvement was significant only when compared with the rest 201Tl images in dual-isotope scintigraphy protocol (75+/-8% vs. 81+/-9% of peak activity, rest vs. 24-hour RD; p<0.01) and not when compared with the 4-hour RD in the 201Tl scintigraphy. On the other hand, when only the segments with severely reduced uptake (<50% of peak activity) were analyzed, the 24-hour RD improved myocardial uptake significantly (p<0.001 vs. rest and vs 4-hour RD) in both protocols. We conclude that a sequential dual-isotope rest 201Tl/stress 99mTc-tetrofosmin scintigraphy is comparable with stress-redistribution 201Tl scintigraphy to detect reversible myocardial hypoperfusion; however in both cases, the addition of 24-hour images increases its usefulness in severely hypoperfused segments, if the uptake of the radiopharmaceutic is quantified.     

Impact of ischemia on left ventricular dyssynchrony by phase analysis of gated single photon emission computed tomography myocardial perfusion imaging

Background

There is increasing awareness of the value of phase analysis of gated tomographic myocardial perfusion imaging in assessing left ventricular (LV) dyssynchrony. A concern repeatedly raised in many studies is whether reversible defects in the stress images “ischemia” could affect the phase-derived standard deviation and bandwidth, the two commonly used dyssynchrony indices. We hypothesized that the stress and rest images should provide comparable information because the images are acquired 1 hour after the tracer injection.

Methods and Results

We studied two groups of patients with normal LV ejection fraction and no fixed perfusion defects. In group-1 (N = 20), the patients had reversible perfusion defects involving > 10% of the LV myocardium and in group-2 (N = 20), the patients had normal images. All patients underwent stress/rest-gated single photon emission computed tomography sestamibi imaging (the stress study was acquired with the lower dose) between January and March 2010. Patients with left bundle branch block or ventricular pacing were excluded. The patients in group-1 had a mean age of 61 ± 9 years, 65% were men, 75% Caucasians, and 70% had known prior coronary artery disease. The size of the reversible perfusion defect was 20 ± 13% (range 11%-50%) of the LV myocardium. The rest and stress phase-derived standard deviation (16 ± 6° vs 18 ± 8° and 16 ± 7° vs. 19 ± 6°) and the rest and stress bandwidth (42 ± 14° vs 46 ± 16° and 45 ± 17° vs 52 ± 12°), respectively, (P = NS for all) were similar in the two groups. The change (stress–rest) in standard deviation and bandwidth in groups 1 and 2 were not statistically significant (0.2 ± 3.1° vs 1.4 ± 4.7°, and 2 ± 13° vs 5 ± 13°, respectively, P = NS). There was no significant change from rest to stress in the standard deviation and the bandwidth in group-1 (P = .8 and .4, respectively) and group-2 (P = .2 and .08, respectively). There was no correlation between the size of the reversible perfusion defect and the change in phase standard deviation or bandwidth (r = 0.07 and 0.12, respectively, P = NS).

Conclusions

The presence of even a large reversible perfusion defect does not alter the indices of mechanical dyssynchrony by phase analysis. Further, comparable information is obtained whether using a low dose or a high dose of the radiotracer.     

Quantitative thallium-201 and technetium 99m sestamibi tomography at rest in detection of myocardial viability in patients with chronic ischemic left ventricular dysfunction

Background  This study was designed to determine the most effective quantitative threshold for thallium-201 and technetium 99m sestamibi uptake on tomographic imaging after rest injection for the detection of myocardial viability in patients with chronic myocardial infarction. Methods and Results  Thallium and sestamibi cardiac tomography at rest was performed in 43 patients with chronic myocardial infarction and impaired left ventricular (LV) function undergoing coronary revascularization. In all patients, echocardiography and radionuclide angiography were performed at baseline and repeated 12 months later to evaluate recovery of regional LV function and LV ejection fraction, respectively. Optimal threshold cutoff points to separate reversible from irreversible dysfunction were determined by receiver operating characteristic analysis. When all dysfunctional segments were considered, the best cutoff point in the identification of reversible LV dysfunction for both thallium and sestamibi activity was 67%. When only akinetic or dyskinetic segments were considered, the best cutoff point in the identification of reversible LV dysfunction was 58% for thallium and 55% for sestamibi. In these segments, the area under the receiving operating characteristic curves constructed for thallium and sestamibi activity were 0.74±0.05 and 0.75±0.04, respectively (P=not significant). LV ejection fraction was 33%±7% at baseline and increased to 37%±7% after revascularization (P<.0001). A significant relation between the number of akinetic or dyskinetic but viable myocardial segments and revascularization-induced changes in LV ejection fraction was observed for both thallium (r=0.60, P<.0001) and sestamibi (r=0.64, P<.0001) imaging. Conclusions  In patients with chronic myocardial infarction, quantitative analysis of thallium and sestamibi activity on tomographic imaging at rest predicts recovery of regional and global LV dysfunction after revascularization procedures. The most effective quantitative threshold for detecting reversible LV dysfunction is comparable for thallium and sestamibi tomographic imaging. However, the optimal cutoff point is different for both tracers when all dysfunctional segments are considered or when the analysis is focused only on segments with more severe functional impairment (ie, akinetic or dyskinetic segments).     

Simultaneous dual-radionuclide myocardial perfusion imaging with a solid-state dedicated cardiac camera

Purpose

We compared simultaneous dual-radionuclide (DR) stress and rest myocardial perfusion imaging (MPI) with a novel solid-state cardiac camera and a conventional SPECT camera with separate stress and rest acquisitions.

Methods

Of 27 consecutive patients recruited, 24 (64.5±11.8 years of age, 16 men) were injected with 74 MBq of ²⁰¹Tl (rest) and 250 MBq ^99mTc-MIBI (stress). Conventional MPI acquisition times for stress and rest are 21 min and 16 min, respectively. Rest ²⁰¹Tl for 6 min and simultaneous DR 15-min list mode gated scans were performed on a D-SPECT cardiac scanner. In 11 patients DR D-SPECT was performed first and in 13 patients conventional stress ^99mTc-MIBI SPECT imaging was performed followed by DR D-SPECT. The DR D-SPECT data were processed using a spill-over and scatter correction method. DR D-SPECT images were compared with rest ²⁰¹Tl D-SPECT and with conventional SPECT images by visual analysis employing the 17-segment model and a five-point scale (0 normal, 4 absent) to calculate the summed stress and rest scores. Image quality was assessed on a four-point scale (1 poor, 4 very good) and gut activity was assessed on a four-point scale (0 none, 3 high).

Results

Conventional MPI studies were abnormal at stress in 17 patients and at rest in 9 patients. In the 17 abnormal stress studies DR D-SPECT MPI showed 113 abnormal segments and conventional MPI showed 93 abnormal segments. In the nine abnormal rest studies DR D-SPECT showed 45 abnormal segments and conventional MPI showed 48 abnormal segments. The summed stress and rest scores on conventional SPECT and DR D-SPECT were highly correlated (r=0.9790 and 0.9694, respectively). The summed scores of rest ²⁰¹Tl D-SPECT and DR-DSPECT were also highly correlated (r=0.9968, p<0.0001 for all). In six patients stress perfusion defects were significantly larger on stress DR D-SPECT images, and five of these patients were imaged earlier by D-SPECT than by conventional SPECT.

Conclusion

Fast and high-quality simultaneous DR MPI is feasible with D-SPECT in a single imaging session with comparable diagnostic performance and image quality to conventional SPECT and to a separate rest ²⁰¹Tl D-SPECT acquisition.